This invention relates in general to high power, semiconductor modules for electrical power generator assemblies, and more particularly, to mobile vehicle electrical generators which are relegated to an insulator fluid coolant for dual functional protection of electrical breakdown isolation and superior heat transfer from the electrical semiconductor fusion elements.
The invention is particularly applicable to aviation, marine, and space mission electrical power generation requirements where consideration of weight, volume, lubricating and cooling fluids becomes problematical because of the volume and weight competition with payload and propellants. This is especially true for extended orbital missions and also for non-recurrent space based missions where there is little or no possibility for rendering a refueling. The barriers presented to successful operations may also be viewed in terms of the measurable powered lifting cost per pound or kilogram of equipment.
Commercial aviation apparatus redundancy for uninterrupted cyclic airport operations, lifting capacity limitations and the expansion of the number of passenger seat miles flown per annum, safely and dependably with economy of operations, are important considerations for all aviation airframe operators. The aviation operations for the government of the U.S., as well as that of other mobile governments in the world, are perceived to be no less demanding in favoring the satisfaction of these requirements. The satisfaction of all of these requirements are usually met with multi-engined aircraft operated such that each engine can be used to power a separate generator system with each generator being capable of fulfilling the entire electrical power output needs for the aircraft.
Each generator system incorporates static electrical power conversion elements which constitute a converter bank of rectifiers in an inverter unit. This unit along with the other units i.e., conversion, filter, heat exchanger and control modules for the generator system, occupies physical space up to a limit usually determined by that available within each engine nacelle assigned space. The weight of same substantially contributes to wing loading up to the capacity of the original gross take-off weight as well as the landing weight. This equipment is relatively fixed over the course of each cycle of departure and landing operations.
In marine utilization of electrical power generators, weight and volume of components are likewise relevant in a set of criteria which dramatize safety and dependability of operations. The size of the payload and coolant tank competition with fuel load are not such apparent competing factors, however, it is possible to perceive that these factors are more relevant when agility and speed in the water are overriding goals, as with the U.S. Navy for both surface and undersea operations. The determination to achieve the maximum power output capability relative to the weight of the unit provides a goal oriented approach to updating components. This leads to downsizing the necessary onboard space and displacement which are part of the design criterion of marine engineering. Another concern is for the retrofitting or replacement of components that are not readily adapted to be changed, and avoiding long periods of shutdown at dockside from the inevitable failures which can occur while at sea, unless this can be postponed or otherwise dealt with by other measures.
Another very special set of design criterion and operational relationships is yet to be completely satisfied for space mission electrical power generation. This is with regard to space based activities such as orbital stations which have some of the same type of problems as do the aviation and marine utilizations. The rule is for more limited replacement capabilities if any are to be provided, and assuredly, if there is not a built in modularity it is with far greater difficulty and expense. Even more severe requirements are set for inherently more expendable type facilities in space that are intended to have limited human maintenance or no visitation over the course of useful life. There can only be remote direction for so long as there is electrical power generation aboard these facilities. The cost of launching any type of nontended satellite still factors the useful payload and supply of rocket propulsion and other fuels as strong competitive factors to limit the size and weight requirements of the electrical power support system. In this type of space environment, rocket fuel is an expendable which is metered and conserved over the course of the mission, but it has not been extended to be useful in all other respects despite its major bulk and weight in the launch systems.
High power semiconductor stacks for electrical power processing assemblies are of the type that produce kilowatts of power, and extend into the range of producing megawatts of power. Currently these are constructed with stacks of large, heavy, high power semiconductor devices, such as versatile "Hockey Puck" packaged fusion elements rated in size according to the electrical power rating with their associated mounting, cooling, insulating and auxiliary systems.
The presently available liquid or water cooled hardware assemblies are too large and heavy for either near or far space mission utilization, and not even projected increases in the electrical rating of these devices will make them attractive for space hardware. There is a limited capacity of electrical power processing requirements which is served by the present technology, but the needs for aerospace, terrestrial aviation, as well as marine requirements will be better served with new and improved high power semiconductor modules for power generator assemblies.
High power semiconductor devices with fluid cooled heat sinks of the type to which the present invention pertain may be seen with reference to U.S. Pat. No. 4,268,850. This reference teaches that a pair of manifolds for containing the flow of a cooling fluid allows for selective interconnection of the interior passageways of heat sinks having adjustable configurable internal fluid passageways. These passageways are used for forced vaporization cooling of contiguous thyristors and other semiconductor devices mounted in a hockey puck package and capable of switching currents of thousands of amperes, particularly in the transmission and distribution of electric power. One of the problems associated with this type of semiconductor assembly is that it does not maximize the dissipation of heat from the hockey puck's internal electrical element which in this case is a thyristor represented as a black horizontal line within the exterior casing elements.
All of the attendant problems of excessive physical size and weight are inherent when hockey puck semiconductors are employed in a vertical stacking assembly which necessitates a levered bolt compression apparatus. This adds to the physical bulk of the stack since it exists to have a larger physical dimension diametrically, and also, it supersedes the length of the stack of devices and heat sinks. The attendant problem of stack assembling is time consuming and tedious because of the apportionment of leveraged torquing between two or more transversely placed bolts used to apply the compression loading.
Another problem with this arrangement is that it does not provide the most efficient heat transfer from the semiconductor electrical function which results from it being cloistered within the exterior support components of the hockey puck. It is thus twice removed from the cooling oil or other medium which is employed for heat dissipation because the transfer must be made to the external intermediate components. This increases the device temperature which results in a lower rating for the device being developed for a given electrical power. Shortening the life of the electrical components results when excessive heat occurs. Replacements are needed, and this is never a desirable situation, especially when the stack of semiconductor elements is not unitized or contained in a packaged module so as to facilitate ease of replacement if some component of the assembly should fail.